Inside Dental Assisting

Sept/Oct 2013, Volume 10, Issue 5

Published by AEGIS Communications

Filling in the Knowledge Gaps on BPA and Mercury

Explore the myths and truths of common components

By Ellen Meyer

With the rise of social media and the increase in the speed of communication today, patients are likely to encounter health information that concerns them and comes from a range of sources. Many will turn to their oral healthcare providers for answers.

In addition to radiation, the issues generating the most “buzz” and patient questions these days are the bisphenol A (BPA) and mercury in dental amalgam. Practitioners who are able to fill in knowledge gaps—and correct misinformation—can help patients make informed choices about their dental care.

BPA

What Is It?

BPA is a chemical that is often characterized as an endocrine disruptor; it has a chemical structure that allows it to act like a weak estrogen hormone.1It is used to produce the polycarbonate plastics and epoxy resins found in a wide variety of products. Polycarbonate plastics are used for goods such as safety equipment, compact discs, medical devices, and food and drink packaging, including, until recently, infant bottles. Epoxy resins are used in some dental sealants and composites as well as in lacquers that coat metal products, including bottle tops, food cans, and water pipes.2 BPA is also found as an easily absorbed free monomer in thermal paper, such as that used in some cash register receipts and tickets.3

The Basis of the Controversy

Concerns are based on numerous studies suggesting a connection to adult illnesses and disorders, including obesity, cardiovascular disease, diabetes, and fertility problems, as well as problems with children’s behavior.1,4 A survey of almost 1,500 adults aged 18 to 74 years in the United States associated higher BPA levels in the urine with a greater probability of being diagnosed with diabetes, cardiovascular disease, or liver enzyme abnormalities. A follow-up to this study noted an increased risk of overall obesity and belly fat in those with higher BPA levels.1

Studies have also showed that BPA can have adverse effects in pediatric patients. A study led by Maserejian compared exposure to bis-GMA–based dental composite restorations with exposure to amalgam and found an association between composite restorations with impaired psychosocial function in children; no adverse psychosocial outcomes were observed with either greater urethane dimethacrylate-based compomer or amalgam treatment levels.4Obesity concerns were raised mainly by a New York University study showing that children with the highest levels of BPA in their urine also had the highest rates of obesity.5

The Official Position

The FDA and the American Dental Association (ADA) have reassessed their original positions on BPA in light of new evidence. Although the FDA had ruled in 2008 that the chemical was safe for all uses, it introduced steps to reduce exposure for children in 2010 and outright banned its use in baby bottles and sippy cups in July 2012, an action taken in response to an American Chemistry Council petition.6,7The US Department of Health and Human Services (HHS) explained that although “BPA is not proven to harm children or adults, these newer studies have led federal health officials to express some concern about the safety of BPA.”6The HHS position includes a call for more research to better understand the potential human health effects of BPA exposure, especially on young children.6

The ADA has previously called concern about potential BPA exposure from dental composites or sealants “unwarranted at this time,” but as of January 30, 2013, it has taken the topic of BPA in dental materials under review.8

Mercury

What Is It?

The least expensive of filling materials, dental amalgam has been used for more than 150 years. It is a mixture of metals comprising liquid mercury and a powdered alloy composed of silver, tin, and copper. Approximately 50% of dental amalgam is elemental mercury, which releases low levels of mercury vapor.9

The Basis of the Controversy

Some individuals have an allergy or sensitivity to mercury or the other components of dental amalgam that causes oral lesions or other contact reactions. The main source of concern revolves around the mercury vapor, however, which is inhaled and absorbed by the lungs.9

As with most substances, the degree of harm caused by mercury in the body is related to the amount to which the patient is exposed. Very low levels generally have no ill effects. At higher levels—for instance, when workers are exposed to mercury through their jobs—it can cause symptoms such as nervousness, fatigue, irritability, memory loss, and headaches.10

Although the mercury in amalgam was once believed to be inert, there is evidence now that mercury vapor is released as these fillings wear.11 Several reviews of the research have concluded that the amount of mercury released from amalgam in the mouth is very low.10 A report from the Health Care Research Collaborative of the University of Illinois at Chicago School of Public Health, the Healthier Hospitals Initiative, and Health Care Without Harm titled “Mercury in Dental Amalgam and Resin-Based Alternatives: A Comparative Health Risk Evaluation” suggests beginning to phase out mercury-containing amalgam. Peter Orris, MD, MPH, a coauthor of the report and professor of occupational and environmental health sciences at the University of Illinois School of Public Health, said, “We found no evidence of a negative effect on patients’ health from either mercury amalgams or the alternatives used in restorations. Yet the alternatives were less hazardous to the general environment and the public’s health.”11

The Official Position

On July 28, 2009, the FDA issued a final regulation in which it reclassified the mercury component of dental amalgam from Class I (low risk) to Class II (moderate risk).Despite this, the agency wrote, “While elemental mercury has been associated with adverse health effects at high exposures, the levels released by dental amalgam fillings are not high enough to cause harm in patients.”12

The ADA responded to the FDA regulation by underscoring its position that dental amalgam is safe, as well as affordable and durable. “Dental amalgam has been studied and reviewed extensively, and has established a record of safety and effectiveness,” the association stated after the ADA Council on Scientific Affairs’ review of the literature on amalgam safety from January 2004 to April 2009. “Based on the results of this review,” the Council said, “the scientific evidence supports the position that amalgam is a valuable, viable, and safe choice for dental patients.”13

Final Thought

The abundance of health care information available to patients can be empowering—but it also open the door for misinformation and concern. Understanding the FDA and ADA official positions for BPA and mercury in dental amalgam can help dentists provide patients with the best evidence-based information available, allowing them to make informed choices about their treatment.